Exercise treadmills are common and available in a variety of configurations. They may be used to perform a number of different exercises, such as aerobics, walking, running, and the like, with the user remaining in a relatively stationary position. Treadmills may also be used for therapy and diagnostic purposes such as cardiovascular stress testing, physical therapy, gait analysis, and the like.
Traditional treadmills generally include single endless belt that is extended between and movable about a pair of rollers. The endless belt may be driven in a motorized fashion, for example by using a roller encircled by an endless chain loop that engages a pinion gear mounted to an axle of a motor drive shaft, which in turn engages a drive sprocket mounted to an axle shaft of at least one of the rollers.
The endless belt of a traditional treadmill is often formed by a rubber material that is sturdy and which has sufficient tensile strength to withstand the forces produced by a user exercising on the treadmill. The endless belt is also often supported along its length and width between the rollers so as to enable the belt to bear the weight of a user. For example, a plurality of support pins or a decking system may be placed contiguous with an underside of the endless belt in order to provide appropriate support.
Typically, the walking surface of the endless belt has a smooth and non-textured finish that is designed to simulate certain a flat and relatively hard surface, such as asphalt or the loop of a track and field stadium. As such, traditional treadmills are unable to leverage the advantages of walking on certain natural surfaces (e.g., sand), which have been shown to increase the energetic cost of walking and running at all speeds.
In addition, the walking surface of a traditional treadmill is relatively hard and non-compliant. As a result, the impact forces generated by a user while exercising on such a treadmill may be substantial. Over time, such impact forces can cause wear and tear on the body, particularly the joints of the lower body. This can limit or prevent some users from exercising on a traditional treadmill. For example, individuals who are injured or who have a chronic condition such as lower back pain or diabetic neuropathy may not be able to tolerate the impact forces generated during exercise on a traditional treadmill.
Traditional treadmills may also be of limited usefulness in physical conditioning and/or rehabilitation programs for certain individuals, such as the elderly, the handicapped, and the obese. Such individuals frequently have limited mobility, and may not be able walk or run on a traditional treadmill at a sufficient rate for weight loss, physical therapy, or another purpose. Moreover, such users often suffer from joint problems and other injuries, which can independently limit the usefulness of a traditional treadmill, as described above.